1. Field of the Invention
The present invention relates to an arc generating electric system adapted for use in a metal casting apparatus, and more particularly, to an arc generating electric system adapted for a metal casting apparatus in which system a high-tension d.c. voltage is employed to generate an electric arc for obtaining a molten metal to be cast in the mold.
2. Description of the Prior Art
It is known in the art to employ electric arc discharges for obtaining a molten metal to be cast in a mold, but it has been found difficult to maintain the electric arc long enough to melt the material under the inert gas atmosphere, because under this atmosphere the gap between two electrodes must be enlarged (e.g. 5 to 10 mm) so as to produce an adequate amount of heat. However, it has proved to be difficult to generate an effectively continuous electric arc in such a large electrode gap.
In order to overcome the difficulty it has been proposed to employ a high-frequency voltage for generating an electric arc. However, the following disadvantages have been encountered:
(1) The polarities of the electrode and the material are continuously reversed as is to be expected from an A.C. current generator, and the electric arc dissipates after a single arcing, thereby failing to generate a continuous electric arc. As a result, it is impossible to enlarge the gap between the electrode and the material,
(2) In order to obtain an enlarged gap, a highly intensified high-frequency voltage can be employed, but it requires sufficient insulation. This results in a large-scale, expensive apparatus, and;
(3) A high-frequency wave may occur, which is likely to invade a power supply and/or to cause an aerial disturbance in the circumstance.
The present invention is directed toward solving the difficulties and disadvantages mentioned above, and has for its object to provide an improved arc generating electric system adapted for use in a metal casting apparatus, wherein the electric system permits the employment of a high-tension d.c. current to maintain the electric arc in effect regardless of a relatively large gap between two electrodes.
Other objects and advantages of the present invention will be obvious to one skilled in the art from the following description.